1. Field
Disclosed herein are off-road tires, in particular civil engineering tires, and their treads. These tires have to have very different technical characteristics from the tires intended for vehicles running on road (that is to say, a bituminous surface), as the nature of the ground on which they are moving is very different and in particular much more aggressive, due to its stony nature. Furthermore, in contrast to passenger vehicle tires, for example, in particular for large civil engineering vehicles, the tires have to be able to withstand a load which can be extremely heavy. Consequently, the solutions known for tires running on a bituminous surface are not directly applicable to off-road tires, such as civil engineering tires.
2. Description of Related Art
Today, the tread of off-road tires generally includes natural rubber, a reinforcing filler of carbon black type and additives normally used for these tires. The manufacturers of off-road tyres are seeking to improve the wear resistance of these tyres and thus their lifetime, without bringing about an increase in the hysteresis. It is possible to use synthetic elastomers as replacement for natural rubber. Such synthetic elastomers bring about an increase in the stiffness of the composition of the tread of the tire, which is unfortunately generally accompanied, for tires running on a non-bituminous or soft surface, of the type of those encountered on the work sites of civil engineering vehicles, by an increase in the hysteresis and thus in the internal temperature of the tire during working. The use of synthetic elastomers in the compositions of treads of off-road tires is thus limited by the increase in the hysteresis, in particular in the case of large-sized tires.
An increase in the stiffness of the composition of the tread of the tire might also be obtained by the use of finer reinforcing fillers or by increasing the content of reinforcing fillers. Unfortunately, this solution brings about, in particular for off-road tires having very large sizes, an increase in the hysteresis and thus does not make it possible to solve the problem set out above.